This invention relates generally to operating gas turbine engines and, more particularly, to a method and systems for providing adaptive ignition for increased stored energy or spark rate at low ambient temperatures.
Ignition system energy requirements for at least some known engines are specified to ensure sufficient energy delivery for all worst case starting scenarios (for example, at cold temperature). This typically means that the system is delivering more energy than necessary during optimal engine starting conditions. Specifying worst case energy requirements for an engine ignition system means that the ignition system is delivering more energy than necessary during optimal (room temperature or higher) engine starting conditions, and that this higher delivered energy (and thus stored energy) imposes a weight penalty on the ignition exciter due to large size and increased weight tank capacitors. This increased energy also has an adverse effect on the exciter tank capacitor life due to increased electrical stress, and igniter plug life due to increased erosion from higher sparking energies. Implementing circuits that simply increase power conversion of the energy storage system, or permit increased energy storage before triggering the ignition spark event during cold temperature conditions are not sufficient as each of these parameters (stored energy and spark rate) have been proven to be critical to successful engine starting. Also, the optimal implementation would permit a reduced delivered energy and spark rate operational mode for typical engine starting performance during room temperature or hot conditions.